1. Field of the invention
This invention relates to a process for making foundry molds for use in metal casting through heating, drying and curing steps, and more particularly to an improved process for making foundry molds which comprises steps of filling a mold pattern with mold sand composed of refractory particles and a water-soluble binding agent added thereto, and then curing the mold sand by exposing it to microwave energy thereby making a foundry mold having a hardened layer on the outer peripheral surface thereof.
2. Description of the prior art
As for processes for making foundry molds for use in metal casting which includes a step of curing mold sand by exposing it to microwave energy, those disclosed, for example, in U.S. Pat. No. 4,518,031 (By Yamanashi et al) and Japanese Patent Application Laid-Open Publication No. 58-187232 etc. have been so far employed.
These publicly known processes each comprise steps of making a foundry mold with wet mold sand composed of refractory material particles to which a binding agent such as, for example, water glass etc. is added and then heating and drying the mold to be cured thus cured by exposing it to microwave energy thereby making a mold having a hardened layer on the outer peripheral surface thereof.
Such prior art processes for making molds have been disadvantageous in that since the mold pattern to form a mold is filled with wet mold sand, the fluidity of the mold sand in the mold pattern is poor, and so in case of making a mold having a complicated shape, it is difficult to fill the mold pattern completely with the mold sand.
Further, for the purpose of forming a hardened layer on the outer peripheral surface of the mold, a method of applying a water-soluble mold wash on the outer peripheral surface of the mold to be cured by means of a brush or by spraying after the fabrication of the mold is disclosed in the Japanese Patent Publication No. 55-29778 (Assignee of which is KABUSHIKI KAISHA KOMATSU SEISAKUSHO). This prior art method has, however, been disadvantageous in that the adhesion of the coating layer to the mold becomes insufficient; the mold tends to be damaged during casting process, and the used mold cannot be easily broken after casting process thus causing inconveniences when the mold is put to reuse.